When yarn is produced in an open-end spinning device of a rotor spinning machine, the spinning fibers are opened into individual fibers and fed to the spinning rotor and pulled off as spun, twisted yarn through a yarn draw-off nozzle centrally arranged in the spinning rotor. In the process, the rotation of the spinning rotor causes the individual fibers to be incorporated in the end of the already produced yarn, which extends as a rotating yarn leg between the rotor groove and the yarn draw-off nozzle, and a twist is imparted to the yarn. Here, the spinning stability of the open-end spinning device depends essentially from the twist of the revolving yarn leg extending between the yarn draw-off nozzle and the rotor groove. In this case, a yarn twist that is too low will always have a negative impact on spinning stability. Therefore, various open-end spinning devices have been known in the state of the art with which twists as false twist can be pushed back towards the spinning rotor against the yarn's draw-off direction. This makes it possible to increase the real twist in the yarn section between the yarn draw-off nozzle and the rotor groove.
DE 40 39 755 A1 shows such a yarn draw-off device of a rotor spinning machine, in which a yarn deflection point is arranged downstream from the yarn draw-off nozzle, and the yarn is drawn off in this deflection point through false twist edges lying obliquely to the yarn path. At the same time, the false twist edges can have a largely circular cross-section and be executed web-like or triangularly. This can generate a false twist that becomes larger as the profile of the false twist becomes more sharp-edged. However, if the false twist becomes too sharp-edged, it can damage the yarn surface, so that a compromise must always be selected in practice between introducing a false twist that is as large as possible but nonetheless able to prevent yarn damage.
Apart from the execution of the profile of the false twist edges, the generation of the false twist is additionally influenced by the yarn's wrapping angle with regard to the false twist edge. Therefore, DE 87 02 807 U1 suggests arranging another deflection or false twist edge downstream from the yarn draw-off nozzle opposite the first false twist edge, to deflect the yarn in a direction other than the one of the previous deflection. As a result of this, the yarn's wrapping angle at the first false twist edge can be increased, thus preventing the yarn from being raised from the false twist edge. As a result of this, the effect of the false twist edge can be improved. Incidentally, however, the introduction of the false twist can also be influenced here by the sharp edge quality of the false twist edges, so that the possibilities of introducing a false twist without damaging the yarn are limited here as well.